<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <meta http-equiv="X-UA-Compatible" content="IE=edge">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>边框</title>

    <style>
        .container{
            width: 300px;
            height: 300px;

            /* 粗细 */
            /* border-right-width: 2px; */
            /* 样式 */
            /* border-right-style: dotted; */
            /* 颜色 */
            /* border-right-color: red; */

            /* border-bottom: 2px solid red; */

            border: 2px solid red;

            border-radius: 50%;
        }
    </style>
</head>
<body>

    <div class="container"></div>
    
</body>
</html>